Optical connection components

Abstract

To provide optical connection components that can reduce optical transmission loss. [Solution] The optical connection component comprises a glass member and an optical waveguide formed inside the glass member and having a higher refractive index than the glass member. In the refractive index distribution of the optical waveguide along the first direction, if the distance from the center to the outer edge of the optical waveguide along the first direction is represented as r, the refractive index at the outer edge of the optical waveguide is represented as nr1.0, the refractive index at a position 20% away from the center of the optical waveguide is represented as nr0.2, and the refractive index at a position 80% away from the center of the optical waveguide is represented as nr0.8, then the ratio of the refractive index nr0.2 to the refractive index n1 (nr0.2 / n1) is 85% or more and 100% or less, and the ratio of the refractive index nr0.8 to the refractive index n1 (nr0.8 / n1) is 8% or more and 75% or less.

Description

Technical Field

[0001] This disclosure relates to optical connection components.

Background Art

[0002] Non-Patent Document 1 to Non-Patent Document 4 disclose techniques for forming optical waveguides by a drawing method using femtosecond laser light. Non-Patent Document 1 discloses a technique for increasing the refractive index inside a glass member by irradiation with femtosecond laser light. Non-Patent Document 2 and Non-Patent Document 4 disclose techniques for forming optical waveguides by single scan drawing of femtosecond laser light. Non-Patent Document 3 discloses a technique for forming an optical waveguide having a square cross-sectional shape by multi scan drawing of femtosecond laser light.

[0003] Non-Patent Document 5 discloses a technique for increasing the refractive index inside a glass member by increasing the pulse energy of femtosecond laser light. Patent Document 1 discloses a technique for forming an optical waveguide using a plurality of branched beams. Patent Document 2 discloses a technique for reducing transmission loss by reducing the fluctuation of the outer diameter of the core.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0005] <00OO033>

Non-Patent Document 1

Outdoor Tool2

Outdoor Tools3

Outdoor Tools 4

Direct Environment 5

[0006] In the technologies described in Non-Patent Documents 1 and 2, the lateral width of the optical waveguide formed inside the glass member is narrow, less than 2 μm, so it does not function as an optical waveguide, or even if light can propagate inside the optical waveguide, the bending loss is large due to the small confinement of light. In contrast, the technology in Non-Patent Document 3 adjusts the lateral width of the optical waveguide by scanning the laser beam 20 times while shifting it in a direction perpendicular to the optical axis of the laser beam. However, this technology has the problem that the time required to form a single optical waveguide is 20 times longer than that of single-scan drawing, so the productivity of optical connection components is significantly reduced. On the other hand, in the technology described in Patent Document 1, a single laser beam is split into multiple diffracted light beams using hologram technology, and multiple optical waveguides are formed simultaneously in a single scan using these multiple diffracted light beams.

[0007] However, in the technologies described in Non-Patent Document 3 and Patent Document 1, the refractive index distribution of the optical waveguide formed by laser irradiation becomes a step-index type, reflecting the abrupt change in the light intensity of the laser light, and the refractive index difference at the boundary between the optical waveguide (core) and the surrounding region (cladding) becomes large. Since the main transmission loss in the optical waveguide is dominated by fluctuations in the shape of the boundary between the core and cladding, caused by fluctuations in the power of the laser light source, pointing deviations, and stage vibrations, there is a risk that the transmission loss will increase as the refractive index difference at the boundary between the core and cladding increases.

[0008] This disclosure provides an optical connection component that can reduce optical transmission loss. [Means for solving the problem]

[0009] An optical connection component in one embodiment of the present disclosure comprises a glass member and an optical waveguide formed inside the glass member and having a higher refractive index than the glass member, wherein in a cross section perpendicular to the direction in which the optical waveguide extends, the width of the optical waveguide along the first direction is equal to or different from the width of the optical waveguide along the second direction perpendicular to the first direction, and in the refractive index distribution of the optical waveguide along the first direction, when the maximum refractive index of the optical waveguide is represented as n1 and the average refractive index of the region of the glass member excluding the optical waveguide is represented as n2, the range of refractive index n2 + 0.01% or more including refractive index n1 When the range of an optical waveguide is defined as nr0.8, and the distance from the center to the outer edge of the optical waveguide along the first direction is denoted as r, the refractive index at the outer edge of the optical waveguide is denoted as nr1.0, the refractive index at a distance of 20% of r from the center of the optical waveguide is denoted as nr0.2, and the refractive index at a distance of 80% of r from the center of the optical waveguide is denoted as nr0.8, then the ratio of refractive index nr0.2 to refractive index n1 (nr0.2 / n1) is between 85% and 100%, and the ratio of refractive index nr0.8 to refractive index n1 (nr0.8 / n1) is between 8% and 75%. [Effects of the Invention]

[0010] The optical connection component described herein can reduce optical transmission loss. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1(a) shows the configuration of a manufacturing apparatus for producing optical connection components according to one embodiment. Figure 1(b) is a diagram illustrating the scanning of laser light by the manufacturing apparatus shown in Figure 1(a). [Figure 2] Figure 2 shows the configuration of the beam forming section of the manufacturing apparatus shown in Figure 1(a). [Figure 3]Fig. 3(a) is a diagram showing the change in the state of the wavefront of the laser light along the major axis direction. Fig. 3(b) is a diagram showing the change in the state of the wavefront of the laser light along the minor axis direction. Fig. 3(c) is a diagram showing the beam irradiation region of the laser light at the focus point. [Figure 4] Fig. 4(a) is a diagram showing the beam irradiation region of the laser light having a flat top-shaped light intensity distribution. Fig. 4(b) is a diagram showing the formation process of the optical waveguide inside the glass member. [Figure 5] Fig. 5 is a perspective view schematically showing the optical connection component manufactured by the manufacturing apparatus of Fig. 1(a). [Figure 6] It is a graph showing the refractive index distribution of the optical waveguide along the major axis direction. [Figure 7] Fig. 7 is a graph showing the relationship between the pulse energy of the laser light and the refractive index difference of the optical waveguide with respect to the glass member. [Figure 8] Fig. 8 is a flowchart for explaining an example of the manufacturing method of the present embodiment. [Figure 9] Fig. 9 is a flowchart for explaining an example of the process included in Fig. 8. [Figure 10] Fig. 10(a) is a diagram showing the change in the state of the major axis wavefront of the laser light formed by the manufacturing apparatus of the comparative example. Fig. 10(b) is a diagram showing the change in the state of the minor axis wavefront of the laser light formed by the manufacturing apparatus of the comparative example. Fig. 10(c) is a diagram showing the beam irradiation region of the laser light condensed by the manufacturing apparatus of the comparative example. [Figure 11] Fig. 11 is a diagram showing the beam cross section along the optical axis direction of the laser light condensed by the manufacturing apparatus of the comparative example. [Figure 12] Fig. 12(a) is a diagram showing the cross-sectional shape of the optical waveguide formed inside the glass member by the manufacturing apparatus of the comparative example. Fig. 12(b) is a diagram showing the shape of the guided mode propagating through the optical waveguide shown in Fig. 12(a). [Figure 13] Fig. 13 is a diagram showing the beam cross section along the optical axis direction of the laser light condensed by the manufacturing apparatus of Fig. 1(a). [Figure 14]Figure 14(a) shows an image of the cross-sectional shape of an optical waveguide formed inside a glass component by the manufacturing apparatus shown in Figure 1(a). Figure 14(b) shows the shape of the waveguide modes propagating through the optical waveguide shown in Figure 14(a). [Modes for carrying out the invention]

[0012] [Description of Embodiments in this Disclosure] First, the embodiments of this disclosure will be listed and explained.

[0013] (1) An optical connection component in one embodiment of the present disclosure comprises a glass member and an optical waveguide formed inside the glass member and having a higher refractive index than the glass member, wherein in a cross section perpendicular to the direction in which the optical waveguide extends, the width of the optical waveguide along the first direction is equal to or different from the width of the optical waveguide along the second direction perpendicular to the first direction, and in the refractive index distribution of the optical waveguide along the first direction, when the maximum refractive index of the optical waveguide is represented as n1 and the average refractive index of the region of the glass member excluding the optical waveguide is represented as n2, the range of refractive index n2+0.01% or higher including refractive index n1 When the bounding box is defined as the range of the optical waveguide, and the distance from the center to the outer edge of the optical waveguide along the first direction is denoted as r, the refractive index at the outer edge of the optical waveguide is denoted as nr1.0, the refractive index at a distance of 20% of the distance r from the center of the optical waveguide is denoted as nr0.2, and the refractive index at a distance of 80% of the distance r from the center of the optical waveguide is denoted as nr0.8, then the ratio of the refractive index nr0.2 to the refractive index n1 (nr0.2 / n1) is between 85% and 100%, and the ratio of the refractive index nr0.8 to the refractive index n1 (nr0.8 / n1) is between 8% and 75%.

[0014] As described above, conventional technology can form optical waveguides with a step-index type refractive index distribution, in which case there is a problem of increased transmission loss due to fluctuations in the optical waveguide caused by the laser light source and optical system. In contrast, the optical connection component described above can make the refractive index distribution of the optical waveguide along the first direction a graded-index type, Gaussian type, or alpha-power type, in which the refractive index difference at the boundary between the optical waveguide (core) and the surrounding region (cladding) is small. In optical waveguides with a refractive index distribution that has such a small refractive index difference, even if fluctuations occur in the optical waveguide caused by the laser light source and optical system, it is possible to reduce the transmission loss due to those fluctuations.

[0015] (2) In the optical connection component described in (1) above, the distance r may be 2 μm or more and 5 μm or less. In this case, an optical waveguide with an appropriate size that can reduce transmission loss can be realized.

[0016] (3) In the optical connection components described in (1) or (2) above, the refractive index difference between refractive index n1 and refractive index n2 may be 0.2% or more and 0.5% or less. In this case, the refractive index difference at the boundary between the optical waveguide (core) and the surrounding region (cladding) can be made smaller, so that transmission loss can be reduced more effectively.

[0017] [Details of the embodiments of this disclosure] Specific examples of optical connection components according to embodiments of this disclosure will be described below with reference to the drawings. This disclosure is not limited to these examples, and all modifications within the meaning and scope of the claims are intended to be included. In the following description, the same elements in the drawings will be denoted by the same reference numerals, and redundant descriptions will be omitted where appropriate.

[0018] Figure 1(a) is a schematic diagram of a manufacturing apparatus 1 for manufacturing the optical connection component 2 of this embodiment. Figure 1(b) is a diagram for explaining the scanning of laser light L by the manufacturing apparatus 1. Each figure shows an XYZ Cartesian coordinate system. The manufacturing apparatus 1 shown in Figure 1(a) manufactures an optical connection component 2 in which an optical waveguide 5 is formed inside a glass member 3 by irradiating the glass member 3 with laser light L. The glass member 3 is, for example, a plate with the Z-axis direction as the thickness direction. Hereinafter, the direction intersecting the Z-axis direction will be referred to as the X-axis direction (second direction), and the direction intersecting both the X-axis direction and the Z-axis direction will be referred to as the Y-axis direction (first direction).

[0019] As shown in Figure 1(a), the manufacturing apparatus 1 comprises a laser light source 10, a laser drive unit 15, a stage 20, a stage drive unit 25, a control unit 30, and a beam shaping unit 40.

[0020] The laser light source 10 emits pulsed laser light L toward the interior of the glass member 3 placed on the stage 20 to form an optical waveguide 5 (see Figure 1(b)). The laser light source 10 is, for example, a femtosecond laser capable of emitting femtosecond laser light as the laser light L. The laser light L has an energy amount that causes a photo-induced refractive index change in the glass member 3 and has a repetition frequency of 10 kHz or higher. Photo-induced refractive index change refers to the refractive index change induced inside the glass member 3 by light irradiation such as laser light L. The refractive index change is defined by the maximum refractive index difference within the light irradiation region where the refractive index change occurred, with the refractive index outside the light irradiation region as the reference. The energy amount that causes a photo-induced refractive index change in the glass member 3 is, for example, 10 5 W / cm 2 This refers to the peak power mentioned above.

[0021] The repetition frequency of the laser light L is, for example, between 10 kHz and 5 MHz. By having a repetition frequency of 10 kHz or higher, the refractive index and structure of the optical waveguide 5 formed inside the glass member 3 can be made smooth. The pulse width of the laser light L is, for example, 500 fs (femtoseconds) or less. The pulse width is defined as the time interval at which the amplitude is 50% of the maximum amplitude. The wavelength of the laser light L is, for example, in the range of -10 nm to +10 nm relative to 1030 nm, in the range of -10 nm to +10 nm relative to 1060 nm, the second harmonic generation (SHG) in each wavelength range, or the third harmonic generation (THG) in each wavelength range.

[0022] The laser drive unit 15 is connected to the laser light source 10 and the control unit 30. The laser drive unit 15 controls the power, pulse width, and repetition frequency of the laser light L emitted from the laser light source 10 according to instructions from the control unit 30. The laser drive unit 15 includes, for example, an electronic circuit including a large integrated circuit. The control unit 30 includes, for example, a computer equipped with a CPU and memory.

[0023] The beam shaping unit 40 is positioned between the laser light source 10 and the glass member 3. The beam shaping unit 40 focuses the laser light L emitted from the laser light source 10 onto a focal point 3p inside the glass member 3 placed on the stage 20, while shaping it into a desired shape. In this embodiment, the laser light L at the focal point 3p is shaped into an elliptical shape (see Figure 3(c)) or a line beam shape in a cross section (hereinafter referred to as the "beam cross section") perpendicular to the optical axis direction of the laser light L incident on the glass member 3, for example, having mutually orthogonal major axis AX1 and minor axis AX2. The light intensity distribution along the major axis AX1 of the laser light L at the focal point 3p is Gaussian or flat-top. The light intensity distribution along the minor axis AX2 of the laser light L at the focal point 3p is Gaussian. The specific configuration of the beam shaping unit 40 will be described later.

[0024] The stage 20 includes a mounting surface 20a on which the glass member 3 is mounted. The mounting surface 20a is movable along the X-axis, Y-axis, and Z-axis directions. The stage 20 can move the glass member 3 relative to the beam forming section 40. The stage drive unit 25 is connected to the control unit 30 and the stage 20. The stage drive unit 25 controls the position of the stage 20 according to instructions from the control unit 30.

[0025] As the stage 20 moves relative to the beam shaping unit 40, the position of the focal point 3p of the laser beam L relative to the glass member 3 also moves. This enables scanning of the laser beam L as shown in Figure 1(b). In the example shown in Figure 1(b), the laser beam L is irradiated onto the glass member 3 in the Z-axis direction, and the focal point 3p of the laser beam L moves along the X-axis direction. In this case, an optical waveguide 5 extending along the X direction is formed inside the glass member 3. Thus, by moving the position of the focal point 3p of the laser beam L relative to the glass member 3, an optical waveguide 5 of any pattern is formed inside the glass member 3.

[0026] Figure 2 shows the configuration of the beam shaping unit 40. As shown in Figure 2, the beam shaping unit 40 includes a magnifying optical system 43, a first beam shaping element D1, a second beam shaping element D2, a reduction optical system 45, an objective lens 47 (focusing lens), a plurality of mirrors 51, 52, 53, 54, 55, and a feedback control mechanism 60A.

[0027] The expanding optical system 43 is positioned on the optical path P1 of the laser beam L emitted from the laser light source 10. The expanding optical system 43 is, for example, a beam expander. The expanding optical system 43 expands the beam diameter of the laser beam L emitted from the laser light source 10 while parallelizing the laser beam L. The beam diameter of the laser beam L expanded by the expanding optical system 43 depends on the size of the first beam shaping element D1, but is, for example, in the range of 5 mm to 30 mm. Two mirrors 51 and 52 are positioned between the expanding optical systems 43. The laser beam L that has passed through the expanding optical system 43 is reflected by the two mirrors 51 and 52 and then guided to the first beam shaping element D1.

[0028] The first beam shaping element D1 is positioned on the optical path P2 of the laser beam L emitted from the magnifying optical system 43. The laser beam L, which has been expanded and parallelized by the magnifying optical system 43, is incident on the first beam shaping element D1. The first beam shaping element D1 shapes the laser beam L such that the width of the beam shape in the long axis direction A1 in the beam cross-section is different from the width of the beam shape in the short axis direction A2. The long axis direction A1 means the direction in which the long axis AX1 extends at the focal point 3p, and before focusing at the focal point 3p, it means the direction in which the axis corresponding to the long axis AX1 extends in any beam cross-section along the optical axis direction of the laser beam. The short axis direction A2 means the direction in which the short axis AX2 extends at the focal point 3p, and before focusing at the focal point 3p, it means the direction in which the axis corresponding to the short axis AX2 extends in any beam cross-section along the optical axis direction of the laser beam.

[0029] In this specification, when "beam shape" is used simply, it means the shape of the beam cross-section at any position along the optical axis of the laser beam. The "beam shape" is such that, at any position along the optical axis of the laser beam, the light intensity of the laser beam L along the long axis A1 and the light intensity of the laser beam L along the short axis A2 are each 1 / e of the maximum light intensity. 2 It is defined by the contour of the region.

[0030] The first beam shaping element D1 shapes the laser beam L into a shape that is elongated in one direction, such as an elliptical or line beam. For example, the first beam shaping element D1 focuses the laser beam L only in the long axis direction A1, making the width of the beam shape in the long axis direction A1 smaller than the width in the short axis direction A2. The first beam shaping element D1 focuses the laser beam L in the long axis direction A1 at the second beam shaping element D2, which is located at a predetermined optical distance from the first beam shaping element D1, such that the ratio of the width of the beam shape in the long axis direction A1 to the width of the short axis direction A2 is, for example, 10. More precisely, since parallel light is formed after the second beam shaping element D2, the first beam shaping element D1 and the second beam shaping element D2 are positioned so that their focal lengths match. The first beam shaping element D1 does not focus the laser beam L in the short axis direction A2, maintaining the laser beam L as parallel light. The first beam shaping element D1 may focus the laser beam L in both the long axis direction A1 and the short axis direction A2. In this case, the first beam shaping element D1 may have a focusing force in the long axis direction A1 greater than the focusing force in the short axis direction A2, such that the width of the beam shape in the long axis direction A1 is smaller than the width of the beam shape in the short axis direction A2.

[0031] The first beam shaping element D1 is, for example, a diffractive optical element (holographic optical element) that includes a phase modulation surface in which multiple pixels are arranged in two dimensions. In this case, the first beam shaping element D1 modulates the phase of the laser light L by the phase pattern (hologram) presented on the phase modulation surface. As a result, the first beam shaping element D1 shapes the beam shape of the laser light L into a shape that is elongated in one direction, such as an elliptical or line beam shape. The first beam shaping element D1 is, for example, an LCoS (Liquid Crystal on Silicon) capable of dynamically switching the phase pattern presented on the phase modulation surface. Hereafter, this variable LCoS will be referred to as LCoS-SLM (Liquid Crystal on Silicon based Spatial Light Modulator).

[0032] The first beam shaping element D1 is electrically connected to the feedback control mechanism 60A and presents a phase pattern on its phase modulation surface corresponding to the correction signals θ1, θ2, θ3, θ4 provided by the feedback control mechanism 60A. The first beam shaping element D1 may modulate the light intensity distribution of the laser light L to a desired light intensity distribution by modulating the phase of the laser light L according to the phase pattern. For example, to make the light intensity distribution along the long axis AX1 of the laser light L at the focal point 3p a flat-top shape, the first beam shaping element D1 may modulate the phase of the laser light L so that the light intensity distribution along the long axis A1 of the laser light L has a distribution shape represented by a sink function. The first beam shaping element D1 emits the shaped laser light L toward the second beam shaping element D2.

[0033] The second beam shaping element D2 is positioned on the optical path P3 of the laser beam L emitted from the first beam shaping element D1. The laser beam L shaped by the first beam shaping element D1 is incident on the second beam shaping element D2. The second beam shaping element D2 shapes the laser beam L so that the wavefront of the laser beam L after shaping by the first beam shaping element D1 becomes a plane.

[0034] The second beam shaping element D2 is, for example, a diffractive optical element (holographic optical element) that modulates the phase of the laser light L by a phase pattern (hologram) presented on the phase modulation surface. The second beam shaping element D2 is, for example, a bulk DOE (Diffractive Optical Element) that statically presents the phase pattern on the phase modulation surface. Static presentation of the phase pattern on the phase modulation surface means that one phase pattern is formed on the phase modulation surface, and that the phase pattern presented on the phase modulation surface is not configured to be switchable. The second beam shaping element D2 modulates the phase of the laser light L by, for example, the phase pattern formed on the phase modulation surface, so that the wavefront of the laser light L becomes planar. The second beam shaping element D2 emits the shaped laser light L toward the reduction optical system 45, which is located a predetermined optical distance away from the second beam shaping element D2.

[0035] The reduction optical system 45 is positioned on the optical path P4 of the laser beam L between the second beam shaping element D2 and the objective lens 47. Two mirrors 53 and 54 are positioned between the second beam shaping element D2 and the reduction optical system 45. The laser beam L emitted from the second beam shaping element D2 is reflected by the two mirrors 53 and 54 and then guided to the reduction optical system 45. The reduction optical system 45 is an optical system that reduces the beam shape of the laser beam L emitted from the second beam shaping element D2 while maintaining the laser beam L as parallel light, and includes, for example, a pair of lenses 45a and 45b. The pair of lenses 45a and 45b are positioned side by side in a direction along the optical axis of the laser beam L reflected by the mirrors 54.

[0036] The reduction optical system 45 reduces the beam shape of the laser light L so that the widths of the beam shape in the long axis direction A1 and the short axis direction A2 are less than or equal to the aperture diameter of the objective lens 47. For example, if the width of the beam shape in the long axis direction A1 of the laser light L is 1, the reduction optical system 45 reduces the width of the long axis direction A1 to a range of 0.1 to 0.9. The reduction optical system 45 emits the reduced laser light L toward the objective lens 47, which is located at a predetermined optical distance from the reduction optical system 45. The reduction optical system 45 is not necessarily required and can be omitted as appropriate.

[0037] The objective lens 47 is positioned on the optical path P5 of the laser beam L between the reduction optical system 45 and the glass member 3. A mirror 55 is positioned between the reduction optical system 45 and the glass member 3. The laser beam L emitted from the reduction optical system 45 is reflected by the mirror 55 and then guided to the objective lens 47. The laser beam L, whose beam shape has been reduced by the reduction optical system 45, is incident on the objective lens 47. The objective lens 47 focuses the laser beam L emitted from the reduction optical system 45 to a focal point 3p inside the glass member 3. The beam shape at the focal point 3p is, for example, an elliptical or line beam shape, which is elongated in one direction. The optical axis of the objective lens 47 is positioned, for example, along the Z-axis direction. Therefore, the laser beam L emitted from the objective lens 47 is incident on the glass member 3 along the Z-axis direction. The numerical aperture (NA) of the objective lens 47 is, for example, 0.1 or more and 1.3 or less. An oil immersion type high NA lens may be used for the objective lens 47.

[0038] Figure 3(a) shows the change in the wavefront state of the laser beam L along the long axis A1. Figure 3(b) shows the change in the wavefront state of the laser beam L along the short axis A2. Figure 3(c) shows the beam irradiation area R of the laser beam L at the focal point 3p. Hereafter, the wavefront of the laser beam L along the long axis A1 will be referred to as the "long axis wavefront AS1", and the wavefront of the laser beam L along the short axis A2 will be referred to as the "short axis wavefront AS2".

[0039] As shown in Figures 3(a) and 3(b), both the long-axis wavefront AS1 and the short-axis wavefront AS2 of the laser beam L directed toward the first beam shaping element D1 (i.e., the laser beam L before focusing to the focal point 3p) are planar. When the laser beam L is incident on the first beam shaping element D1, the first beam shaping element D1 shapes the laser beam L so that it is focused along the long axis A1. At this time, as shown in Figure 3(a), the long-axis wavefront AS1 of the laser beam L changes from a planar to a concave surface. On the other hand, as shown in Figure 3(b), the first beam shaping element D1 maintains the short-axis wavefront AS2 of the laser beam L as a planar surface. As a result, the beam shape of the laser beam emitted from the first beam shaping element D1 is shaped to be elongated in one direction.

[0040] Next, as shown in Figures 3(a) and 3(b), when the laser beam L is incident on the second beam shaping element D2, the second beam shaping element D2 shapes the laser beam L so that both the long-axis wavefront AS1 and the short-axis wavefront AS2 are planar. Specifically, when the first beam shaping element D1 focuses the long-axis wavefront AS1 of the laser beam L, the second beam shaping element D2 modulates the phase of the laser beam L so that the long-axis wavefront AS1, which has changed to a concave shape, becomes planar, while maintaining the short-axis wavefront AS2 as a plane. However, if the short-axis wavefront AS2 is not strictly maintained as a plane, the second beam shaping element D2 may modulate the phase of the laser beam L so that both the long-axis wavefront AS1 and the short-axis wavefront AS2 are strictly planar.

[0041] Subsequently, the laser beam L is incident on the objective lens 47 with both the long-axis wavefront AS1 and the short-axis wavefront AS2 in a planar state. The objective lens 47 focuses the laser beam L to the focal point 3p. As shown in Figures 3(a) and 3(b), the width of the beam shape in the long-axis direction A1 of the laser beam L incident on the objective lens 47 is smaller than the width of the beam shape in the short-axis direction A2. For example, the width of the beam shape in the long-axis direction A1 is smaller than the aperture diameter of the objective lens 47, and the width of the beam shape in the short-axis direction A2 is the same as the aperture diameter of the objective lens 47. In this case, the objective lens 47 focuses the laser beam L in the short-axis direction A2 to the diffraction limit. On the other hand, since the width of the beam shape in the long-axis direction A1 is smaller than the aperture diameter of the objective lens 47, the objective lens 47 cannot completely focus the laser beam L in the long-axis direction A1.

[0042] Therefore, the objective lens 47 focuses the laser beam L more in the minor axis direction A2 than in the major axis direction A1. As a result, the width W1 in the major axis direction A1 of the beam shape of the laser beam L after focusing by the objective lens 47 is relatively larger than the width W2 in the minor axis direction A2 of the beam shape after focusing to the diffraction limit. Consequently, the beam shape at the focusing point 3p becomes an ellipse with a minor axis AX2 and a major axis AX1, as shown in Figure 3(c). The beam shape of the laser beam L at the focusing point 3p corresponds to the beam irradiation area R shown in Figure 3(c). Note that at the focusing point 3p, the major axis direction A1 coincides with the Y axis direction, and the minor axis direction A2 coincides with the X axis direction.

[0043] The beam irradiation region R shown in Figure 3(c) is, for example, elliptical in shape, having a minor axis AX2 and a major axis AX1 that is longer than the minor axis AX2. The major axis AX1 and the minor axis AX2 are axes perpendicular to the optical axis direction of the laser beam L and are orthogonal to each other. The length of the major axis AX1 corresponds to the width W1 of the beam irradiation region R along the major axis direction A1. The length of the minor axis AX2 corresponds to the width W2 of the beam irradiation region R along the minor axis direction A2. The length of the major axis AX1 is longer than the length of the minor axis AX2. The ratio of the length of the major axis AX1 to the length of the minor axis AX2, i.e., the ratio of the width W1 along the major axis direction A1 of the beam irradiation region R to the width W2 along the minor axis direction A2 of the beam irradiation region R (W1 / W2), is, for example, between 2 and 20, and in one example, it is 10.

[0044] If the laser beam L is simply focused into an elliptical shape or the like without any adjustment to its light intensity distribution during the process of passing through the first beam shaping element D1, the second beam shaping element D2, and the objective lens 47, the light intensity distribution of the laser beam L along the long axis A1 and the short axis A2 at the focal point 3p will be Gaussian in shape. On the other hand, if the first beam shaping element D1 adjusts the light intensity distribution of the laser beam L along the long axis A1 to a shape represented by a sink function, the light intensity distribution of the laser beam L along the long axis A1 at the focal point 3p will be converted to a flat-top shape. The light intensity distribution of the laser beam L along the short axis A2 at the focal point 3p may also be Gaussian in shape.

[0045] Figure 4(a) shows the beam irradiation region R of a laser beam L having a flat-top shaped optical intensity distribution. Figure 4(b) shows the formation process of the optical waveguide 5 inside the glass member 3. Figure 4(a) shows both the optical intensity distribution LD1 in the long axis direction A1 of the laser beam L and the optical intensity distribution LD2 in the short axis direction A2 of the laser beam L, and these optical intensity distributions LD1 and LD2 define the flat-top shape of the beam irradiation region R. In the beam irradiation region R, the optical intensity of these optical intensity distributions LD1 and LD2 is 1 / e of the maximum optical intensity. 2It is defined by the contour of the region. In the region with a flat top shape, if r is the distance from the center position of the major axis A1, the full width at half maximum of the light intensity distribution LD1 along the major axis A1 is 2W, and the maximum light intensity of the light intensity distribution LD1 is P, then the light intensity is 0.9P or greater in the range -0.9W ≤ r ≤ 0.9W, and 0.1P or less in the range r ≤ -1.1W or 1.1W ≤ r.

[0046] As shown in Figure 4(b), the width W1 along the long axis A1 of the beam irradiation region R is adjusted to obtain the width Wx of the optical waveguide 5 to be formed. The width W2 along the short axis A2 of the beam irradiation region R is adjusted to obtain the desired amount of refractive index change in the beam irradiation region R. By moving the focal point 3p of the laser beam L along the X axis (scanning direction) inside the glass member 3, the optical waveguide 5 is formed inside the glass member 3 in a single scan. The width W1 along the long axis A1 of the beam irradiation region R contributes to the width Wy of the optical waveguide 5, while the width W2 along the short axis A2 of the beam irradiation region R contributes to the amount of refractive index change inside the glass member 3. In addition to adjusting the amount of refractive index change, the width W2 along the short axis A2 of the beam irradiation region R can also be used to adjust the width Wx in the thickness direction (Z axis direction) of the optical waveguide 5. When the light intensity distribution along the long axis A1 of the laser beam L at the focal point 3p is Gaussian in shape, the slope of the light intensity distribution is gentle. In this case, by narrowing the width W2 in the short axis A2 of the beam irradiation region R, the sum of the light intensity distributions in the long axis A1 and the short axis A2 can exceed the modification threshold that determines the width Wx of the optical waveguide 5. As a result, the width Wx of the optical waveguide 5 is expanded.

[0047] Refer again to Figures 3(a) and 3(b). As shown in Figures 3(a) and 3(b), in this embodiment, before the laser beam L is incident on the objective lens 47, the second beam shaping element D2 adjusts the long-axis wavefront AS1 and the short-axis wavefront AS2 of the laser beam L so that they are both planar. In this case, the curvature of both the long-axis wavefront AS1 and the short-axis wavefront AS2 are maintained at zero, so there is no difference in curvature between the long-axis wavefront AS1 and the short-axis wavefront AS2, or the difference is extremely small. When such a laser beam L is focused by the objective lens 47, the focusing position fp1 of the laser beam L with respect to the long-axis direction A1 coincides with or is near the focusing position fp2 of the laser beam L with respect to the short-axis direction A2. The focusing position fp1 of the laser beam L with respect to the long-axis direction A1 is the position of the beam waist that occurs in the light intensity distribution of the laser beam L along the long-axis direction A1. The focusing position fp2 of the laser beam L relative to the short axis direction A2 is the position of the beam waist that occurs in the light intensity distribution of the laser beam L along the short axis direction A2.

[0048] Therefore, in this embodiment, there is no or extremely small deviation in the optical axis distance between the focusing position fp1 of the laser beam L relative to the long axis A1 and the focusing position fp2 of the laser beam L relative to the short axis A2. For example, the difference in the optical axis distance between the focusing position fp1 of the laser beam L relative to the long axis A1 and the focusing position fp2 of the laser beam L relative to the short axis A2 is 0 μm to 10 μm. As the deviation between focusing positions fp1 and fp2 becomes smaller, the distortion of the laser beam shape caused by astigmatism is reduced.

[0049] However, in reality, the state of the laser beam L can change over time due to the influence of fluctuations in the laser light source 10, disturbances from the optical system, and vibrations of the stage 20 during the process from the laser light source 10 to the objective lens 47. Therefore, as described above, in order to reduce astigmatism and shape the beam into the desired shape, it is effective to correct the state of the laser beam L directed toward the objective lens 47 in real time. Accordingly, in this embodiment, the beam shaping unit 40 is further equipped with a feedback control mechanism 60A (see Figure 2) for correcting the state of the laser beam L in real time.

[0050] As shown in Figure 2, the feedback control mechanism 60A includes a feedback controller 60, a first sensor S1, a second sensor S2, a third sensor S3, a fourth sensor S4, a plurality of samplers 61, 62, 63, 64, an objective lens 65, and an observation objective lens 66.

[0051] The feedback controller 60 is a computer including a processor, memory, etc. The feedback controller 60 executes various control functions using the processor. The feedback controller 60 may be integrated with the control unit 30 or may be separate from the control unit 30. The feedback controller 60 is connected to each sensor S1, S2, S3, S4 in a communicative manner and acquires beam information φ1, φ2, φ3, φ4 acquired by each sensor S1, S2, S3, S4. The beam information φ1, φ2, φ3, φ4 is information indicating the state of the laser beam L. At least one of the beam information φ1, φ2, φ3, φ4 includes, as described later, the radius of curvature of the wavefront of the laser beam L, the size of the beam shape of the laser beam L, the incident position of the laser beam L, and the incident angle of the laser beam L.

[0052] The feedback controller 60 may be connected to each sensor S1, S2, S3, and S4 by wire or by wireless connection, as long as it is possible to transfer information to each sensor S1, S2, S3, and S4. Furthermore, the feedback controller 60 is electrically connected to the first beam shaping element D1 and controls the phase pattern presented to the first beam shaping element D1 in real time using the beam information φ1, φ2, φ3, and φ4 from each sensor S1, S2, S3, and S4. In other words, the feedback controller 60 feeds back the beam information φ1, φ2, φ3, and φ4, which indicate the state of the laser light L, to the first beam shaping element D1. The feedback controller 60 only needs to be in a state where it can supply signals and power to the first beam shaping element D1, and may be indirectly connected to the first beam shaping element D1 by other components in between.

[0053] The first sensor S1 detects a portion of the laser light L directed from the magnifying optical system 43 toward the first beam shaping element D1 as the first observation light L1. A sampler 61 is positioned on the optical path P2 of the laser light L between the magnifying optical system 43 and the first beam shaping element D1. The first sensor S1 is positioned on the optical path of the first observation light L1 reflected by the sampler 61. Therefore, the first sensor S1 is optically coupled to the optical path P2 of the laser light L between the magnifying optical system 43 and the first beam shaping element D1. The first sensor S1 is positioned in a position that is optically conjugate to the first beam shaping element D1. The first observation light L1 reflected by the sampler 61 is incident on the first sensor S1.

[0054] The first sensor S1 acquires beam information φ1 indicating the state of the laser light L on the irradiation surface irradiated onto the first beam shaping element D1, which is beam information indicating the state of the first observation light L1. The position where the first sensor S1 is installed is a position conjugate to the first beam shaping element D1. The distance between the sampler 61 and the first sensor S1 is the same as the distance between the sampler 61 and the first beam shaping element D1. The first beam information φ1 includes, for example, the radius of curvature of the major axis wavefront AS1 and the minor axis wavefront AS2 of the laser light L, the size of the beam shape of the laser light L, the incident angle of the laser light L on the first beam shaping element D1, and the incident position of the laser light L on the first beam shaping element D1. The size of the beam shape of the laser light L is the beam diameter of the laser light L on the irradiation surface irradiated onto the first beam shaping element D1.

[0055] The first sensor S1 includes a wavefront sensor that detects the radius of curvature of the major-axis wavefront AS1 and the minor-axis wavefront AS2 of the laser light L, and a CCD camera that detects the size of the beam shape of the laser light L. The wavefront sensor and the CCD camera may be installed interchangeably at the same location, or they may be installed at different locations. If the wavefront sensor and the CCD camera are installed at different locations, the first observation light L1 reflected by the sampler 61 can be split by a half mirror or the like, provided that the distance between the sampler 61 and the first beam shaping element D1, the distance between the sampler 61 and the wavefront sensor, and the distance between the sampler 61 and the CCD camera are the same. The first sensor S1 provides the first beam information φ1 to the feedback controller 60. The first sensor S1 may also acquire the first beam information φ1 using the reflected light from a permanently installed sampler.

[0056] The feedback controller 60 corrects the phase pattern of the first beam shaping element D1 using the first beam information φ1. The phase pattern of the first beam shaping element D1 is designed on the premise that the laser light L is incident on the first beam shaping element D1 in a parallel state. However, in reality, the laser light L may be incident on the first beam shaping element D1 with at least one of the long-axis wavefront AS1 and the short-axis wavefront AS2 not being planar, but convex or concave. In this case, it is expected that the beam shape and light intensity distribution of the laser light L emitted from the first beam shaping element D1 will deviate from the desired beam shape and light intensity distribution due to the effect of curvature. Therefore, the feedback controller 60 performs a correction to eliminate the effect of fluctuations in the curvature of the laser light L incident on the first beam shaping element D1.

[0057] For example, the feedback controller 60 acquires the radius of curvature included in the first beam information φ1 with a resolution of 10 mm, and corrects the phase pattern of the first beam shaping element D1 so as to cancel out the curvature of the wavefront AS1 and AS2 of the laser light L directed toward the first beam shaping element D1 if at least one of these wavefronts is not planar. Specifically, the feedback controller 60 applies a phase pattern designed to be the opposite phase of the wavefront of the laser light L to the first beam shaping element D1. This eliminates the effect of the curvature of the laser light L incident on the first beam shaping element D1. Canceling out the curvature of the wavefront of the laser light L means canceling out the curvature of the wavefront of the laser light L, that is, flattening the wavefront of the laser light L.

[0058] Furthermore, when the feedback controller 60 corrects the phase pattern of the first beam shaping element D1, it adjusts the phase pattern so that the size of the laser beam shape (i.e., beam diameter) of the laser light L matches the aperture diameter of the first beam shaping element D1. For example, the feedback controller 60 acquires the size of the beam shape included in the first beam information φ1 with an accuracy of 0.1 mm and corrects the phase pattern of the first beam shaping element D1 so that the size of the beam shape matches the aperture diameter of the first beam shaping element D1. The feedback controller 60 may also correct the size of the laser light L beam shape to match the aperture diameter of the first beam shaping element D1.

[0059] Accordingly, the feedback controller 60 outputs a first correction signal θ1 to the first beam shaping element D1, which corrects the phase of the laser beam L so that the curvature of the laser beam L is canceled out and the size of the beam shape of the laser beam L is less than or equal to the aperture of the first beam shaping element D1. The first beam shaping element D1 corrects the phase of the laser beam L according to the first correction signal θ1, thereby correcting the curvature of at least one of the wavefronts AS1 (long axis wavefront) and AS2 (short axis wavefront) of the laser beam L, and correcting the size of the beam shape of the laser beam L to be less than or equal to the aperture diameter of the first beam shaping element D1.

[0060] The second sensor S2 detects a portion of the laser light L traveling from the first beam shaping element D1 to the second beam shaping element D2 as the second observation light L2. A sampler 62 is positioned on the optical path P3 of the laser light L between the first beam shaping element D1 and the second beam shaping element D2. The second sensor S2 is positioned on the optical path of the laser light L reflected by the sampler 62. Therefore, the second sensor S2 is optically coupled to the optical path P3 of the laser light L between the first beam shaping element D1 and the second beam shaping element D2. The second sensor S2 is positioned in a position that is optically conjugate to the second beam shaping element D2. The second observation light L2 reflected by the sampler 62 is incident on the second sensor S2.

[0061] The second sensor S2 acquires beam information indicating the state of the second observation light L2 as second beam information φ2 indicating the state of the laser light L directed toward the second beam shaping element D2. The second beam information φ2 includes, for example, the radius of curvature of the major axis wavefront AS1 and the minor axis wavefront AS2 of the laser light L, the size of the beam shape of the laser light L, the incident position of the laser light L on the second beam shaping element D2, and the incident angle of the laser light L on the second beam shaping element D2. The size of the beam shape of the laser light L is the width A1 in the major axis direction of the laser light L after shaping by the first beam shaping element D1, and the width A2 in the minor axis direction of the laser light L after shaping by the first beam shaping element D1.

[0062] The second sensor S2 includes a wavefront sensor that detects the radius of curvature of the major-axis wavefront AS1 and the minor-axis wavefront AS2 of the laser beam L, and a CCD camera that detects the size of the beam shape of the laser beam L and the incident position of the laser beam L on the second beam shaping element D2. The wavefront sensor and the CCD camera may be installed interchangeably at the same position, or, like the first sensor S1, they may be installed at different positions. The second sensor S2 provides the second beam information φ2 to the feedback controller 60. The second sensor S2 may acquire the second beam information φ2 using reflected light from a permanently installed sampler.

[0063] The feedback controller 60 uses the second beam information φ2 to check the state of the laser beam L emitted from the first beam shaping element D1. For example, the feedback controller 60 checks whether the phase pattern of the first beam shaping element D1 has been properly corrected by the first correction signal θ1. Furthermore, the feedback controller 60 checks whether the incident position of the laser beam L on the second beam shaping element D2 is shifted from the reference position. The reference position is, for example, the central coordinate position of the second beam shaping element D2. The phase pattern of the first beam shaping element D1 is designed on the premise that the laser beam L is incident on the reference position of the second beam shaping element D2. Therefore, if the laser beam L is incident on a position shifted from the reference position of the second beam shaping element D2, it is expected that the beam shape and light intensity distribution of the laser beam L emitted from the second beam shaping element D2 will deviate from the desired beam shape and light intensity distribution. Therefore, the feedback controller 60 performs a correction to compensate for the shift in the incident position of the laser beam L on the second beam shaping element D2.

[0064] For example, the feedback controller 60 outputs a second correction signal θ2 to the first beam shaping element D1, which superimposes a deflection angle component onto the phase pattern of the first beam shaping element D1 so as to reduce the deviation of the incident position of the laser beam L relative to the reference position of the second beam shaping element D2. The first beam shaping element D1 corrects the phase of the laser beam L according to the second correction signal θ2, thereby correcting the incident position of the laser beam L to match the reference position of the second beam shaping element D2.

[0065] The feedback controller 60 may correct the incident angle of the laser beam L to the first beam shaping element D1 so as to reduce the deviation of the incident position of the laser beam L relative to the reference position of the second beam shaping element D2. The feedback controller 60 may perform both correction by superimposing a deflection angle component onto the phase pattern of the first beam shaping element D1 and correction of the incident angle of the laser beam L to the first beam shaping element D1. The deviation of the incident position of the laser beam L relative to the reference position of the second beam shaping element D2 may be corrected with an accuracy of, for example, 1 μm or less or 0.5 μm or less. The incident angle of the laser beam L to the first beam shaping element D1 may be corrected with an accuracy of, for example, 0.1°.

[0066] The third sensor S3 detects a portion of the laser light L traveling from the reduction optical system 45 towards the objective lens 47 as the third observation light L3. A sampler 63 is positioned on the optical path P5 of the laser light L between the reduction optical system 45 and the objective lens 47. For example, the same type of objective lens 65 as the processing objective lens 47 is used. The objective lens 65 is positioned on the optical path of the laser light L reflected by the sampler 63. The objective lens 65 is positioned in a position that is optically conjugate to the objective lens 47. The third sensor S3 is positioned on the optical axis of the objective lens 65 and acquires the focusing state of the objective lens 65 using the observation objective lens 66. Therefore, the third sensor S3 is optically coupled to the optical path P5 of the laser light L between the reduction optical system 45 and the objective lens 47. The third observation light L3 reflected by the sampler 63 enters the third sensor S3 via the objective lens 65 and the observation objective lens 66.

[0067] The third sensor S3 includes, for example, a CCD camera. The third sensor S3 acquires beam information indicating the state of the third observation light L3 as third beam information φ3 indicating the state of the laser light L directed toward the objective lens 47. The third beam information φ3 includes, for example, the light intensity distribution along the optical axis of the laser light L. The light intensity distribution along the optical axis of the laser light L is observed with an accuracy of, for example, 1 μm or less.

[0068] The feedback controller 60 uses the third beam information φ3 to check whether or not astigmatism occurs in the laser beam L focused by the objective lens 47. Specifically, the feedback controller 60 checks whether or not there is a shift in the optical axis direction between the focusing position fp1 of the laser beam L with respect to the long axis direction A1 (see Figure 3(a)) and the focusing position fp2 of the laser beam L with respect to the short axis direction A2 (see Figure 3(b)). If a shift occurs between these focusing positions fp1 and fp2, the feedback controller 60 outputs a third correction signal θ3 to the first beam shaping element D1 to correct the phase of the first beam shaping element D1 so that the shift is reduced.

[0069] For example, the feedback controller 60 may correct the radius of curvature of the long-axis wavefront AS1 of the laser beam L to the negative or positive side if the short-axis wavefront AS2 of the laser beam L is planar. More specifically, if the radius of curvature of the short-axis wavefront AS2 of the laser beam L is large, such as 10 m, and can be considered planar, the feedback controller 60 may shift the radius of curvature of the long-axis wavefront AS1 to the negative or positive side with a resolution of 10 cm. This makes it possible to adjust the deviation of the focusing positions fp1 and fp2 to a desired range. The first beam shaping element D1 corrects the phase of the laser beam L according to the third correction signal θ3, thereby correcting the deviation of the focusing positions fp1 and fp2.

[0070] The fourth sensor S4 detects a portion of the laser light L traveling from the reduction optical system 45 towards the objective lens 47 as the fourth observation light L4. A sampler 64 is positioned on the optical path P5 of the laser light L between the reduction optical system 45 and the objective lens 47. The fourth sensor S4 is positioned on the optical path of the fourth observation light L4 reflected by the sampler 64. Therefore, the fourth sensor S4 is optically coupled to the optical path P5 of the laser light L between the reduction optical system 45 and the objective lens 47. The fourth sensor S4 is positioned in a position that is optically conjugate to the objective lens 47. The fourth observation light L4 reflected by the sampler 64 is incident on the fourth sensor S4.

[0071] The fourth sensor S4 acquires beam information indicating the state of the fourth observation light L4 as fourth beam information φ4 indicating the state of the laser light L directed toward the objective lens 47. The fourth beam information φ4 includes, for example, the radius of curvature of the major axis wavefront AS1 and the minor axis wavefront AS2 of the laser light L incident on the objective lens 47, and the size of the beam shape of the laser light L directed toward the objective lens 47. The size of the beam shape of the laser light L is the width in the major axis direction A1 of the laser light L after it has been shaped by the second beam shaping element D2 and passed through the reduction optical system 45, and the width in the minor axis direction A2 of the laser light L after it has been shaped by the second beam shaping element D2.

[0072] The fourth sensor S4 includes a wavefront sensor that detects the radius of curvature of the major-axis wavefront AS1 and the minor-axis wavefront AS2 of the laser beam L, and a CCD camera that detects the size of the beam shape of the laser beam L. The wavefront sensor and the CCD camera may be installed in the same position, alternating with each other, or they may be installed in different positions, similar to the first sensor S1, the second sensor S2, and the third sensor S3. The fourth sensor S4 provides the fourth beam information φ4 to the feedback controller 60. The fourth sensor S4 may acquire the fourth beam information φ4 using reflected light from a permanently installed sampler.

[0073] The feedback controller 60 uses the fourth beam information φ4 to check whether the long-axis wavefront AS1 and the short-axis wavefront AS2 of the laser beam L directed toward the objective lens 47 are planar. If at least one of the long-axis wavefront AS1 and the short-axis wavefront AS2 of the laser beam L is not planar, the feedback controller 60 corrects the phase pattern of the first beam shaping element D1 to cancel out the curvature of that wavefront. Specifically, the feedback controller 60 outputs a fourth correction signal θ4 to the first beam shaping element D1, which causes the first beam shaping element D1 to apply a phase pattern designed with the opposite phase of the wavefront of the laser beam L. By correcting the phase of the laser beam L according to the fourth correction signal θ4, the first beam shaping element D1 performs a correction that cancels out the curvature of at least one of the long-axis wavefront AS1 and the short-axis wavefront AS2 of the laser beam L.

[0074] Figure 5 is a schematic perspective view of an optical connection component 2 manufactured using the manufacturing apparatus 1. As shown in Figure 5, the optical connection component 2 comprises a glass member 3 and an optical waveguide 5 formed inside the glass member 3. The glass member 3 is, for example, a plate-shaped member with the Z-axis direction as the thickness axis. The glass member 3 includes a first end face 3a and a second end face 3b aligned along the X-axis direction. The first end face 3a and the second end face 3b are, for example, planes extending along the X-axis direction and the Y-axis direction. The first end of the optical waveguide 5 is exposed from the first end face 3a. The second end of the optical waveguide 5 is exposed from the second end face 3b.

[0075] The glass component 3 is formed from a glass material such as phosphate glass (P2O5 glass) or silicate glass (SiO2 glass). In one example, the glass component 3 is made of phosphate glass or silicate glass containing additives. The glass component 3 may contain Ge (germanium) or B (boron) as additives. In this case, these additives may be uniformly distributed throughout the glass component 3.

[0076] The optical waveguide 5 formed inside the glass member 3 is a region of continuous refractive index change induced by light. The refractive index change region is formed by focusing pulsed laser light L inside the glass member 3 and continuously moving the focusing point 3p. The optical waveguide 5 extends linearly along the X-axis direction from the first end face 3a to the second end face 3b, for example. The optical waveguide 5 may have a three-dimensional solid structure that changes in the X-axis direction, Y-axis direction, and Z-axis direction inside the glass member 3. In a cross section perpendicular to the X-axis direction (i.e., the optical axis direction of the optical waveguide 5) along which the optical waveguide 5 extends, the shape of the optical waveguide 5 is, for example, a rectangular shape with the Y-axis direction as the longitudinal direction. The width Wy of the optical waveguide 5 along the Y-axis direction may be the same as the width Wx of the optical waveguide 5 along the X-axis direction (Wy=Wx), or it may be longer than the width Wx of the optical waveguide 5 (Wy>Wx), or shorter than the width Wx of the optical waveguide 5 (Wy <Wx)てもよい。

[0077] Figure 6 is a graph showing the refractive index distribution G1 of the optical waveguide 5 along the Y-axis. The vertical axis of Figure 6 represents the refractive index n of the optical waveguide 5 along the Y-axis, and the horizontal axis of Figure 6 represents the position of the optical waveguide 5 along the Y-axis. The shape of the refractive index distribution G1 of the optical waveguide 5 along the Y-axis is not the common step-index type, but a Gaussian type as shown in Figure 6. The shape of the refractive index distribution G1 may also be a graded-index type or an α-power type. In the refractive index distribution G1 shown in Figure 6, if we represent the maximum value of refractive index n as n1, and the average value of refractive index n in the region of the glass member 3 that is not irradiated by laser light L (i.e., the region of the glass member 3 excluding the optical waveguide 5) as n2, then the range of n2 + 0.01% or more, including refractive index n1, can be defined as the range of the optical waveguide 5. In this case, the position where the refractive index n is n2 + 0.01% can be defined as the outer edge of the optical waveguide 5. Then, the position of refractive index n1 can be defined as the center of the optical waveguide 5.

[0078] In Figure 6, if r is the distance from the center to the outer edge of the optical waveguide 5 along the Y-axis, then the distance r is, for example, between 2 μm and 5 μm. If the refractive index n at the outer edge of the optical waveguide 5 is defined as refractive index nr1.0, the refractive index nr0.2 at a distance of 20% of the distance r from the center of the optical waveguide 5 is defined as refractive index nr0.8, then the ratio of refractive index nr0.2 to refractive index n1 (nr0.2 / n1) is, for example, between 85% and 100%, and the ratio of refractive index nr0.8 to refractive index n1 (nr0.8 / n1) is, for example, between 8% and 75%. The refractive index difference between refractive index n1 and refractive index n2 is, for example, between 0.2% and 0.8%. When using an optical connection component 2 equipped with an optical waveguide 5 having the refractive index distribution G1 shown in Figure 6, the transmission loss is, for example, less than 0.1 dB / cm.

[0079] Figure 7 shows the relationship between the pulse energy of the laser beam L and the refractive index difference of the optical waveguide 5 (core) relative to pure silica (cladding), which is an example of the material of the glass component 3. Figure 7 shows the results obtained under the following laser beam L irradiation conditions. Average output: 10mW or more and 500mW or less Focusing diameter: 1 μm Pulse width: 150fs or more, or 300fs or less Wavelength: 515nm Repetition frequency: 100kHz to 2MHz Scanning speed: 1 μm / sec to 3000 μm / sec As shown in Figure 7, it can be seen that the refractive index difference tends to increase as the pulse energy of the laser light L increases. If we represent the pulse energy as x and the refractive index difference as y, the approximate equation (relationship) showing the relationship between pulse energy x and refractive index difference y is expressed as y = 0.0168x - 0.3354, and Figure 7 shows the approximation line G2 shown by this approximation formula. The light intensity distribution in the Y-axis direction of the laser light L irradiated onto the glass member 3 is designed using the refractive index distribution G1 in Figure 6 and the approximation line G2 in Figure 7. For example, if the distance r is 2 μm, the focusing diameter is 1 μm, so the desired refractive index is set as n1 = 0.4%, nr0.5 = 0.3%, and nr1.0 = 0.1% for the radial coordinates (horizontal axis in Figure 6) of 0 μm, 1 μm, and 2 μm. Then, by determining the desired pulse energy from the approximation line G2 described above, and multiplying that pulse energy by the repetition frequency under the irradiation conditions described above, the required optical power can be determined.

[0080] Next, the manufacturing method carried out using the manufacturing apparatus 1 described above will be explained with reference to Figures 8 and 9. Figure 8 is a flowchart illustrating an example of the manufacturing method of this embodiment. Figure 9 is a flowchart illustrating an example of the process included in Figure 8.

[0081] First, in the preparation step, the glass member 3, which will become the optical connection component 2, is prepared (step P10 in Figure 8). The glass member 3 is placed on the mounting surface 20a of the stage 20.

[0082] Next, in the laser irradiation process, laser light L is irradiated into the interior of the glass member 3 (step P20 in Figure 8). At this time, the output of the laser light L is set to a level at which modification begins, the focal point is aligned with the surface of the glass member 3, and a height reference in the Z-axis direction is set. Next, in order to avoid unnecessary modification, the glass member 3 is removed from the processing area. The control unit 30 controls the laser drive unit 15 so that laser light L having an energy amount that causes a photo-induced refractive index change inside the glass member 3 and a repetition frequency of 10 kHz or higher is output from the laser light source 10. After confirming that the laser light L emitted from the laser light source 10 has been shaped into the desired beam shape by the beam shaping unit 40, it is focused at the focal point 3p inside the glass member 3. As a method for confirming whether or not the desired beam shape has been formed, for example, the following method can be considered. First, in step P10 (preparation step), the output power of the laser light L is reduced. Then, while shifting the position of the observation objective lens 66, which is incident on the reflected light from the sampler 63 (third observation light L3), in the Z-axis direction, the depth of focus of the beam shaping and the intensity distribution of the laser light L are confirmed.

[0083] In the laser irradiation process, first, the laser light source 10 emits laser light L toward the glass member 3 (step P21 in Figure 9). The laser light L emitted from the laser light source 10 is magnified by the magnification optical system 43 and then incident on the first beam shaping element D1.

[0084] Next, the first beam shaping element D1 shapes the laser beam L such that the width of the beam shape in the long axis direction A1 is different from the width in the short axis direction A2 (step P22 in Figure 9). For example, the first beam shaping element D1 focuses the laser beam L in the long axis direction A1, making the width of the beam shape in the long axis direction A1 smaller than the width in the short axis direction A2. The laser beam L focused in the long axis direction A1 by the first beam shaping element D1 is then incident on the second beam shaping element D2.

[0085] Next, the second beam shaping element D2 shapes the laser beam L so that both the long-axis wavefront AS1 and the short-axis wavefront AS2 are planar (step P23 in Figure 9). The laser beam L, whose long-axis wavefront AS1 and short-axis wavefront AS2 have been adjusted to be planar by the second beam shaping element D2, is reduced by the reduction optical system 45 before being incident on the objective lens 47.

[0086] Next, the objective lens 47 focuses the laser beam L to the focal point 3p inside the glass member 3 so that the beam shape at the focal point 3p has a minor axis AX2 and a major axis AX1 (step P24 in Figure 9). At this time, the laser beam L is focused by the objective lens 47 in the minor axis direction A2 to the diffraction limit. As a result, the width of the beam shape of the focused laser beam L in the major axis direction A1 is relatively larger than the width of the beam shape in the minor axis direction A2, and the beam shape at the focal point 3p inside the glass member 3 is formed into an elliptical or line beam shape with a minor axis AX2 and a major axis AX1. Then, a photoinduced change in refractive index occurs in the beam irradiation region R at the focal point 3p.

[0087] Once the laser irradiation of the glass member 3 is complete through the above laser irradiation process, the control unit 30 controls the stage drive unit 25 to move the position of the glass member 3 placed on the mounting surface 20a of the stage 20 (step P30 in Figure 8). Specifically, the control unit 30 moves the position of the laser beam L's focal point 3p inside the glass member 3 by continuously or intermittently changing the installation position of the glass member 3, the position of the laser beam L's focal point 3p, or both of these positions.

[0088] Next, the control unit 30 determines whether the irradiation of the glass member 3 with laser light L has finished by determining whether the pre-designed pattern of the optical waveguide 5 has been formed inside the glass member 3 by steps P20 and P30 (step P40 in Figure 8). If the control unit 30 determines that the irradiation of the laser light L has not finished (NO in step P40 in Figure 8), it returns to point A in Figure 8 and repeats steps P20 and P30. On the other hand, if the control unit 30 determines that the irradiation of the laser light L has finished (YES in step P40 in Figure 8), it determines that the formation of the optical waveguide 5 in the glass member 3 is complete. After that, in order to suppress changes in the refractive index of the glass member 3 over a long period of time, heat treatment for aging is performed on the glass member 3 (step P150 in Figure 8). Through the above steps, an optical connection component 2 (see Figure 5) with an optical waveguide 5 formed inside the glass member 3 is obtained.

[0089] The effects of the manufacturing apparatus 1 of this embodiment, as described above, will be explained along with the problems of the comparative example.

[0090] Figure 10(a) shows the change in the state of the long-axis wavefront AS101 of the laser beam L formed by the manufacturing apparatus of the comparative example. Figure 10(b) shows the change in the state of the short-axis wavefront AS102 of the laser beam L formed by the manufacturing apparatus of the comparative example. Figure 10(c) shows the beam irradiation region R100 of the laser beam L focused by the manufacturing apparatus of the comparative example.

[0091] In the examples shown in Figures 10(a) to 10(c), the laser beam L is shaped by the beam shaping element 110 and then focused by the objective lens 111. As a result, the beam irradiation area R100 of the focused laser beam L takes on an elliptical shape with a major axis AX101 and a minor axis AX102, as shown in Figure 10(c).

[0092] As shown in Figures 10(a) and 10(b), the beam shaping element 110 focuses the laser beam L in the long axis direction A1, while maintaining the laser beam L as parallel light without focusing it in the short axis direction A2. In this case, the short axis wavefront AS102 of the laser beam L is planar, while the long axis wavefront AS101 of the laser beam L is concave with a certain radius of curvature. When the laser beam L is incident on the objective lens 111 with the curvature of the short axis wavefront AS102 and the long axis wavefront AS101 not matching, a large shift ΔZ occurs between the focusing position fp101 of the laser beam L relative to the long axis direction A1 and the focusing position fp102 of the laser beam L relative to the short axis direction A2 due to the effect of this difference in curvature. In other words, the laser beam L after focusing by the objective lens 111 exhibits large astigmatism.

[0093] Figure 11 shows a beam cross-section along the optical axis of the laser beam L focused by the manufacturing apparatus of the comparative example. In Figure 11, the beam cross-section R101 of the laser beam L along the Z-axis direction (optical axis) and the Y-axis direction (long axis A1) and the beam cross-section R102 of the laser beam L along the Z-axis direction (optical axis) and the X-axis direction (short axis A2) are shown superimposed. Figure 12(a) shows the cross-sectional shape of the optical waveguide 105 formed inside the glass member 3 by the manufacturing apparatus of the comparative example. Figure 12(b) shows the shape of the waveguide mode M100 propagating through the optical waveguide 105 shown in Figure 12(a). Figure 12(a) shows the etching image after polishing the cross-section of the optical waveguide 105 of the glass member 3. The purpose of etching is to make it easier to recognize the cross-sectional shape of the modified region, the optical waveguide 105, by utilizing the difference in etching rate ratio between the region modified by irradiation with laser beam L and the unmodified region.

[0094] As shown in Figure 11, beam cross section R101 shows the focal point fp101, which is the position of the beam waist of the laser light L in the Y-axis direction. Beam cross section R102 shows the focal point fp102, which is the position of the beam waist of the laser light L in the X-axis direction. Focusing point fp102 is significantly shifted from focusing point fp101 along the Z-axis direction. In this case, modification by irradiation with laser light L progresses not only at focusing point fp101 but also at focusing point fp102, resulting in the cross-sectional shape of the optical waveguide 105 becoming an inverted bell shape extending in the Z-axis direction, which is the optical axis direction, as shown in Figure 12(a). In other words, the cross-sectional shape of the optical waveguide 105 has a rectangular cross-sectional region R105a, as well as a cross-sectional region R105b that extends from cross-sectional region R105a in the Z-axis direction, resulting in a shape that is significantly distorted from a rectangular shape. As the cross-sectional shape of the optical waveguide 105 deforms, the waveguide mode M100 propagating through the optical waveguide 105 becomes significantly deformed from a perfect circle, as shown in Figure 12(b). When an optical connection component with such an optical waveguide 105 is connected to a target component such as an SMF, the optical coupling efficiency decreases, and the optical transmission loss increases.

[0095] Figure 13 shows a beam cross-section of the laser beam L focused by the manufacturing apparatus 1 of this embodiment, along the optical axis direction. In Figure 13, the beam cross-section R1 of the laser beam L along the Z-axis direction (optical axis direction) and the Y-axis direction (long axis direction A1) and the beam cross-section R2 of the laser beam L along the Z-axis direction (optical axis direction) and the X-axis direction (short axis direction A2) are shown superimposed. Furthermore, Figure 13 also shows an observation image of the light intensity distribution along the Z-axis direction. Figure 14(a) shows an image of the cross-sectional shape of the optical waveguide 105 formed inside the glass member 3 by the manufacturing apparatus 1 of this embodiment. Figure 14(b) shows the shape of the waveguide mode M propagating through the optical waveguide 105 shown in Figure 14(a).

[0096] In this embodiment, as described above, before the laser beam L is focused by the objective lens 47, the laser beam L is shaped so that both the long-axis wavefront AS1 and the short-axis wavefront AS2 are planar. In this case, the difference between the radius of curvature of the long-axis wavefront AS1 and the radius of curvature of the short-axis wavefront AS2 can be reduced, thereby reducing the astigmatism caused by these differences. In other words, as shown in Figure 13, the focusing position fp1, which is the beam waist position of the laser beam L in the Y-axis direction, coincides with or is formed very close to the focusing position fp2, which is the beam waist position of the laser beam L in the X-axis direction. In other words, in this embodiment, there are no two focusing positions fp1 and fp2 that are far apart along the Z-axis direction. In this case, as shown in Figure 13, the focusing point 3p, where the light intensity of the laser beam L is maximum, is formed at only one location.

[0097] As the modification by irradiation with laser light L progresses at one location along the Z-axis, the cross-sectional shape of the optical waveguide 5 formed by the laser light L can be made to have only a rectangular cross-sectional region R5, as shown in Figure 14(a), that is, a shape that excludes the portion corresponding to the cross-sectional region R105b of the optical waveguide 105 in the comparative example. As a result, as shown in Figure 14(b), the waveguide mode M propagating through the optical waveguide 5 can be made to approach a perfect circle. Thus, according to this embodiment, the risk of the modified region inside the glass member 3 being stretched in the optical axis direction due to irradiation with laser light L can be reduced, and the deformation of the cross-sectional shape of the optical waveguide 5 formed inside the glass member 3 can be reduced. As a result, the deformation of the waveguide mode M propagating inside the optical waveguide 5 can be reduced, and transmission loss can be reduced.

[0098] Next, we will explain the effects of the optical connection component 2 manufactured by the manufacturing apparatus 1 of this embodiment.

[0099] In conventional technology, optical waveguides with a step-index type refractive index distribution may be formed, in which case transmission loss may increase due to fluctuations in the optical waveguide caused by the laser light source and optical system. In contrast, in the optical connection component 2 of this embodiment, the refractive index distribution G1 of the optical waveguide 5 along the Y-axis direction can be made into a graded-index type, in which the refractive index difference at the boundary between the optical waveguide 5 (core) and the surrounding region (cladding) is reduced. In an optical waveguide 5 having such a small refractive index difference in refractive index distribution G1, even if fluctuations occur in the optical waveguide 5 due to the laser light source 10 and optical system, it is possible to reduce transmission loss due to those fluctuations.

[0100] As in this embodiment, the distance r may be 2 μm or more and 5 μm or less. In this case, an optical waveguide 5 with an appropriate size that can reduce transmission loss can be realized.

[0101] As in this embodiment, the refractive index difference between refractive index n1 and refractive index n2 may be 0.2% or more and 0.5% or less. In this case, the refractive index difference at the boundary between the optical waveguide 5 (core) and the surrounding region (cladding) can be made smaller, thus more effectively reducing transmission loss.

[0102] As in this embodiment, the light intensity distribution of the laser beam L along the long axis A1 in the beam shape at the focal point 3p may be set using an approximation line G2 that shows the relationship between the pulse energy of the laser beam L and the refractive index difference of the optical waveguide 5 with respect to the glass member 3, and the refractive index distribution G1 of the optical waveguide 5 along the Y axis. In this case, by irradiating the glass member 3 with laser beam L, an optical waveguide 5 having a refractive index distribution G1 with a small refractive index difference can be easily formed as described above.

[0103] The optical connection components of this disclosure are not limited to the embodiments described above and can be modified without departing from the spirit of the claims. In the embodiments described above, the case in which the first beamforming element D1 is an LCoS-SLM and the second beamforming element D2 is a bulk DOE was described. However, both the first beamforming element D1 and the second beamforming element D2 may be LCoS-SLMs. Alternatively, the first beamforming element D1 may be a bulk DOE and the second beamforming element D2 may be an LCoS-SLM. One of the first beamforming element D1 and the second beamforming element D2 may be a concave lens or a convex lens. Therefore, the combination of the first beamforming element D1 and the second beamforming element D2 is not limited to the combination of an LCoS-SLM and a bulk DOE, but may be a combination of two LCoS-SLMs, an LCoS-SLM and a concave lens, or a convex lens and an LCoS-SLM.

[0104] The arrangement of optical elements included in the beam shaping section is not limited to the example shown in Figure 2. The number, size, and arrangement of optical elements such as the first beam shaping element and the second beam shaping element can be appropriately changed according to the required specifications. In Figure 2, the case in which the feedback control mechanism 60A includes a first sensor S1, a second sensor S2, a third sensor S3, and a fourth sensor S4 is described, but it is not necessary to include all of the first sensor S1, second sensor S2, third sensor S3, and fourth sensor S4, and some sensors may be omitted. Alternatively, the feedback control mechanism 60A may further include other sensors in addition to the first sensor S1, second sensor S2, third sensor S3, and fourth sensor S4. [Explanation of Symbols]

[0105] 1...Manufacturing equipment 2… Optical connection components 3…Glass components 3a...first end surface 3b…Second end face 3p…Focus point 5,105...Optical waveguide 10… Laser light source 15…Laser drive unit 20… Stage 20a… Mounting surface 25…Stage drive unit 30…Control Unit 40...Beam forming section 43…Magnification Optical System 45...Reducing optical system 45a, 45b… lenses 47…Objective lens (focusing lens) 51, 52, 53, 54, 55…Mirror 61, 62, 63, 64… Sampler 60A...Feedback control mechanism 60…Feedback controller 65…Objective lens 66… Observation objective lens 110... Beam forming 111... Objective lens A1…Long axis direction A2…Short axis direction AS1,AS101…long axis wavefront AS2,AS102…Short axis wavefront AX1, AX101…Long axis AX2, AX102…Short axis D1...First beam forming element D2...Second beam forming element fp1, fp2, fp101, fp102… Light-gathering positions G1…Refractive index distribution G2…Approximate line (relationship formula) L... Laser light L1...First observation light L2...Second observation light L3...Third observation light L4…Fourth observation light LD1,LD2…Light intensity distribution n, n1, n2, nr0.2, nr0.8, nr1.0… refractive index M, M100… Navigation Modes P1,P2,P3,P4,P5…light path r... distance R, R100… Beam irradiation area R1, R2, R101, R102... Beam section R5, R105a, R105b…Cross-sectional area S1...First sensor S2...Second sensor S3...Third sensor S4...Fourth sensor W1, W2, Wx, Wy… width θ1…First correction signal θ2…Second correction signal θ3…Third correction signal θ4…Fourth correction signal φ1…First beam information φ2…Second beam information φ3…Third beam information φ4…Fourth beam information

Claims

1. Glass components and The optical waveguide is formed inside the glass member and has a higher refractive index than the glass member, In a cross-section perpendicular to the direction in which the optical waveguide extends, the width of the optical waveguide along the first direction is equal to or different from the width of the optical waveguide along the second direction perpendicular to the first direction. In the refractive index distribution of the optical waveguide along the first direction, if the maximum refractive index of the optical waveguide is represented as n1, and the average refractive index of the region of the glass member excluding the optical waveguide is represented as n2, then the range of the optical waveguide is defined as the range of the optical waveguide including the refractive index n1 and the refractive index n2 + 0.01% or greater. When the distance from the center to the outer edge of the optical waveguide along the first direction is denoted as r, the refractive index at the outer edge of the optical waveguide is denoted as nr1.0, the refractive index at a position 20% of the distance r from the center of the optical waveguide is denoted as nr0.2, and the refractive index at a position 80% of the distance r from the center of the optical waveguide is denoted as nr0.8, The ratio of the refractive index nr0.2 to the refractive index n1 (nr0.2 / n1) is 85% or more and 100% or less. The ratio of the refractive index nr0.8 to the refractive index n1 (nr0.8 / n1) is 8% or more and 75% or less. Optical connection component.

2. The aforementioned distance r is between 2 μm and 5 μm. The optical connection component according to claim 1.

3. The refractive index difference between the refractive index n1 and the refractive index n2 is 0.2% or more and 0.5% or less. The optical connection component according to claim 1.

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